The purification of glutathione-S-transferases from human tissue and rat tissue has been carried out using GSH-affinity chromatography. The relationship among the multiple forms is being studied as is the ketosteroid isomerase activity of the transferases. Specific studies to be carried out are: 1) determine the kinetic parameters of the enzyme - especially with respect to the question of the possible involvement of negative cooperativity; 2) analyze the unusual salt effects on the enzyme.